org.eclipse.viatra2.gtasm.interpreter.impl/src/org/eclipse/viatra2/gtasm/interpreter/impl/rules/ConditionalRuleInterpreter.java

/*******************************************************************************
 * Copyright (c) 2004-2008 Peter Pasztor, Akos Horvath, Gergely Varro, Istvan Rath and Daniel Varro
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Peter Pasztor, Akos Horvath, Gergely Varro, Istvan Rath - initial API and implementation
 *******************************************************************************/

package org.eclipse.viatra2.gtasm.interpreter.impl.rules;


import org.eclipse.viatra2.gtasm.interpreter.exception.ViatraTransformationException;
import org.eclipse.viatra2.gtasm.interpreter.executionEnvironment.IExecutionEnvironment;
import org.eclipse.viatra2.gtasm.interpreter.term.rules.TermEvaluator;
import org.eclipse.viatra2.gtasmmodel.gtasm.metamodel.asm.simpleRules.ASMRuleInvocation;
import org.eclipse.viatra2.gtasmmodel.gtasm.metamodel.asm.simpleRules.ConditionalRuleIf;
import org.eclipse.viatra2.gtasmmodel.gtasm.metamodel.asm.simpleRules.ConditionalRuleTry;
import org.eclipse.viatra2.interpreters.IProgressReport;


public class ConditionalRuleInterpreter extends RuleInterpreter {

	private static ConditionalRuleInterpreter _instance = new ConditionalRuleInterpreter();

	private ConditionalRuleInterpreter() {
		;
	}

	public static ConditionalRuleInterpreter getInstance() {
		return _instance;
	}

	public Boolean interpretRule(IExecutionEnvironment executionEnvironment,
			ASMRuleInvocation ruleToBeInterpreted, IProgressReport pr)
			throws ViatraTransformationException {

		Boolean condition = null;

		/*
		 * This long line is a concise form of determining whether the rule is
		 * an if or a try type rule. In case it is an if type, the condition
		 * term is evaluated, in the other case, the rule is interpreted.
		 * Thereafter the appropriate rule is interpreted.
		 */

		condition = (ruleToBeInterpreted instanceof ConditionalRuleIf) ? (TermEvaluator.getInstance().evaluate(
						executionEnvironment,
						((ConditionalRuleIf) ruleToBeInterpreted)
								.getExpressionToTest()).equals(Boolean.TRUE))
				: (RuleInterpreter.getInstance().interpretRule(
						executionEnvironment,
						((ConditionalRuleTry) ruleToBeInterpreted)
								.getRuleToTry(),pr));

		if (condition.equals(Boolean.TRUE)) {
			return (ruleToBeInterpreted instanceof ConditionalRuleIf) ? 
					(RuleInterpreter.getInstance().interpretRule(executionEnvironment,
					((ConditionalRuleIf) ruleToBeInterpreted).getRuleTrue(),pr))
					: Boolean.TRUE;
		} else {
			ASMRuleInvocation elseRule = (ruleToBeInterpreted instanceof ConditionalRuleIf) ? (((ConditionalRuleIf) ruleToBeInterpreted)
					.getRuleFalse())
					: (((ConditionalRuleTry) ruleToBeInterpreted).getRuleElse());

			if (elseRule == null)
				return Boolean.TRUE;

			return RuleInterpreter.getInstance().interpretRule(
					executionEnvironment, elseRule,pr);
		}
	}
}